Fuel injection is metered into cylinders to provide a desired power output of an engine. Specifically, fuel may be provided to cylinder in the engine via direct injection and/or port injection. However, fuel may flow past the piston into a crankcase housing engine oil. This fuel may contaminate oil in the engine. This contaminated engine oil may affect various engine systems such as the engine lubrication system as well as the PCV and fuel delivery system. Specifically, fuel (e.g., fuel vapor) from the crankcase may flow through the PCV system into an engine intake conduit. This fuel vapor may not be accounted for in the fuel injection system, which may lead to inefficient and degraded combustion operation which may result in misfires, stalls (e.g., rich stalls), hesitations (e.g., lean hesitations at tip-in) etc.
U.S. Pat. No. 8,302,578 discloses a system and method for determining oil fuel dilution in a diesel engine. If the oil fuel dilution surpasses a threshold amount an oil change indicator may be switched on. The inventors have recognized several disadvantages with system and method disclosed in U.S. Pat. No. 8,302,578. Firstly, a vehicle operator may not notice or in some cases disregard an oil change indicator for an extended period of time. As a result, engine lubrication may be degraded during this period of engine operation. Moreover, engine's using positive crankcase ventilation (PCV) systems may also be impacted via oil dilution from engine fuel slipping past the piston during combustion. Fuel may slip past the piston via fuel remaining on the walls of the cylinder during combustion. Therefore, unmetered fuel passing through the PCV system may cause a number of undesirable engine operations such as stalls, degraded starts, delays during start-up, etc. This problem may be exacerbated when fuels with alcohol are used, such as ethanol blends (e.g., E10, E85, and E100). This problem may also be of particular concern in hybrid vehicles where the engine may only be operated for a limited duration during vehicle travel. Therefore, the oil may be contaminated by a large amount of fuel before the oil is sufficiently heated to allow for evaporation of the fuel from the oil. As a result, the oil may have degraded performance and combustion may be reduced in such engines from unmetered fuel entering the intake and cylinder as the oil heats up evaporating the diluted fuel.
The inventors herein have recognized the above issues and developed a method for controlling an internal combustion engine based on fuel dilution in engine oil comprising adjusting fuel injection into a cylinder from a fuel injector in a fuel delivery system based on an amount of engine oil fuel dilution of oil stored in an oil reservoir, the amount of engine oil fuel dilution determined based on one or more of oil volume, oil temperature, engine temperature, engine speed, and engine load. In this way, oil dilution via fuel may be accounted for when determining an amount of fuel injected into a combustion chamber. As a result, combustion efficiency is increased and the likelihood of misfires and stalls are reduced.
The method may further include selectively flowing positive crankcase ventilation (PCV) gas into an intake system of the internal combustion engine from a PCV system, in some examples. Further in some examples, adjusting fuel injection into the cylinder based on the amount of engine oil fuel dilution includes adjusting fuel injection into the cylinder based on an amount of fuel evaporating from the oil and participating in combustion via the PCV system. In this way, the likelihood of combustion degradation during PCV purge operation can be reduced, thereby improving combustion operation.
The above advantages and other advantages, and features of the present description will be readily apparent from the following detailed description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Additionally, the above issues have been recognized by the inventors herein, and are not admitted to be known.